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The Edexcel C3 (14/06/12 - AM) Revision Thread

Reply 1280

wam-bam

1

Original post by suncake

.

Original post by Arva

.

she probably means like an acronym or something :tongue:

OT: do you do chemistrY??

(edited 11 years ago)

Reply 1281

suncake

14

Original post by raheem94

Well done at C1 :smile:

Good luck for the exam

Thank youuu! Good luck for whatever exams you're doing :biggrin:

Reply 1282

Arva

14

Original post by 12win12

any way to remember whether its +/- for sin or cos differenciated?? :/

Yes. If you differentiate sin it becomes cos. If you differentiate cos it becomes -sin.
You can then guess what happens to -sin, since it's -d(sinx)/dx... etc.

Reply 1283

riversandroads93

Original post by UWS

Can someone quickly explain to me how to do question 8c for Jan 2012? I don't understand it...

You divide both sides by (sqrt3 - tanθ)

this will then give you the same equation that you see in part B and it will mean that the result you get on the left hand side is equal to tan(θ + π / 6)

NOTE: The π symbol is pi
this then gives you:

tan(θ + π / 6) = tan(π - θ)

you can then assume that (as these would both equal each other and cancel out):

θ + (π / 6) = π - θ

adding θ to both sides and subtracting (π / 6) from both sides you get:

2θ = (5π / 6)

Divide both sides by two and you get:

θ = (5π / 12)

that's your first answer, and since the range is now 2θ you have to find the second value, this is done by using the same initial equation but inserting 2π instead of π like this:

tan(θ + π / 6) = tan(2π - θ)

and then you do the same working again.
I hope this is clear enough.

Reply 1284

suncake

14

Original post by Jetblast

Yes, but what are these simple methods? I have a multitude of examples, but cant find them now

The domain of f(x) is the range of f^-1(x)
The range of f(x) is the domain of f^-1(x)

(correct me if I'm wrong, Arva :tongue:

)

Reply 1285

icedragon

Original post by Arva

You couldn't do that for the two marker before it though. Less than 10% of candidates got it right - it was the first time it'd turned up in a paper and threw a lot of people. Luckily I think I'm prepared for if something like that comes up.

You were given y = arccos(x). So you know x = cos(y). Therefore arcsin(x) is simply arcsin(cos(y)). That gave you full marks, you didn't have to put it in terms of pi. I'm suprised people struggled with it.

Reply 1286

Arva

14

Original post by Jetblast

Yes, but what are these simple methods? I have a multitude of examples, but cant find them now

I can't really give you a method without a question... :colonhash:

If it gives you the domain, sub in the x values to find out the range. If it gives you either the range or domain of the inverse, you can use those to determine the range or domain of the original.

Reply 1287

docwannabe

Original post by Arva

No problem. Did you get the right answer

(\frac{\pi}{2}-y)

?

Yeah thanks :smile:

Reply 1288

wam-bam

1

Original post by suncake

The domain of f(x) is the range of f^-1(x)
The range of f(x) is the domain of f^-1(x)

(correct me if I'm wrong, Arva :tongue:

)

that's perfect suncake :tongue:

Reply 1289

Arva

14

Original post by suncake

The domain of f(x) is the range of f^-1(x)
The range of f(x) is the domain of f^-1(x)

(correct me if I'm wrong, Arva :tongue:

)

That's right, don't worry. :smile:

Reply 1290

Arva

14

Original post by docwannabe

Yeah thanks :smile:

Reply 1291

Nnaemeka

Well goodluck everyone

Reply 1292

suncake

14

Original post by wam-bam

that's perfect suncake :tongue:

Original post by Arva

That's right, don't worry. :smile:

Woooo!

What are the chances of remainder theorem coming up? (Please say very low)

Reply 1293

wam-bam

1

Original post by suncake

Woooo!

What are the chances of remainder theorem coming up? (Please say very low)

i love remainder theorem :biggrin:

Reply 1294

Arva

14

Original post by suncake

Woooo!

What are the chances of remainder theorem coming up? (Please say very low)

Low, that's usually C2. What's your problem with it though?
Literally just sub in the given X value and the number spat out is your remainder.

Reply 1295

icedragon

Original post by suncake

Woooo!

What are the chances of remainder theorem coming up? (Please say very low)

Even if it does you can just use long division to find the remainder, shouldn't be penalised. Besides, just remember that if you divide a polynomial by (x-c) the remainder will be f(c).

Reply 1296

Chris P Chicken.

[QUOTE="wam-bam;38100405"]

Original post by docwannabe

jan 07 Q8

Ew, that question is fking nasty.
I wouldn't of had a clue what to do if that came up in the exam, since I've never done anything with Arcsin/cos/tan before, at least I know now.